Pool Bucket Test Calculator
A bucket test gives you two marks and a tape measure, and the arithmetic is where people talk themselves out of a real leak or into a fake one. Put in both drops and this reads them the way the bucket test guide does.
Length × width for a rectangle. 16 × 32 is 512.
Pump on its normal schedule
How far each dropped from its mark. A quarter inch is 0.25, an eighth 0.125.
Pump off, if you ran it again
Optional. A second run with the pump off says where the leak is.
Autofill off before you start. Nobody swims, backwashes or tops up during the test, and a rainy day means starting again.
Result
Enter how far each one dropped
The fields start on ordinary values so you can see what each one wants. Nothing is worked out until you put your own numbers in.
A bucket test gives you two marks and a tape measure, and the arithmetic is where people talk themselves out of a real leak or into a fake one. Put in both drops and this reads them the way the bucket test guide does.
Getting an accurate answer
- Turn the autofill off before the test, not after. An autofill tops the pool up as it drops, which reads as the pool losing less than the bucket.
- Measure each drop from its own mark: the bucket from the mark inside it, the pool from the mark outside.
- An eighth of an inch either way is inside the error of reading a tape against a mark. If the answer lands close to that, run the test for 48 hours.
- Run it twice if you can, once with the pump on its normal schedule and once with it off. The difference between the two runs is what says where the leak is.
How the answer is worked out
The bucket sits in the pool, so it has the same air, sun and water temperature, and loses water to evaporation at very nearly the same rate. Only the pool can also be leaking. So the leak is the pool's drop minus the bucket's drop, and the bucket test guide covers how to set it up so that stays true.
Gallons come from spreading that depth over the surface. An inch over a square foot is a twelfth of a cubic foot, and a cubic foot is 7.48 gallons. Half an inch on a 16 by 32 pool works out as 512 × 0.5 ÷ 12 × 7.48 = 160 gallons a day.
A 48-hour run is divided back to a day, so the answers always read per day whichever length you ran.
Why an eighth of an inch is the line
Two marks read against a tape each carry a little error, and an eighth of an inch either way over a day is inside it. A pool that drops a sixteenth more than the bucket has not proven anything.
Running for 48 hours is the fix for a close call. The evaporation and the leak both double, and the error in reading the marks does not, so a marginal result usually turns into a clear one.
What the evaporation figure tells you
The bucket's drop is your evaporation, and it is worth a look on its own. A quarter to half an inch a day is ordinary in hot, dry, windy weather. That is still a lot of water: on a 16 by 32 pool, half an inch is about 160 gallons a day with nothing wrong at all.
More than half an inch a day usually means heat. A heater running without a cover can do it, and a cover is the lever there, not a leak search.
When the pool drops less than the bucket
It cannot, on its own. Something added water to the pool or took extra from the bucket, and the test has to be run again once that is fixed.
The autofill was on. It is almost always this. It rained, and runoff from the deck reached the pool. The bucket sat warm, on the deck or in the sun on a shallow step, and evaporated faster than the pool. Any of the three can also hide a real leak, which is why they matter.
Questions about this calculator
How do I read a pool bucket test?
Subtract the bucket's drop from the pool's. Within about an eighth of an inch is the same drop, and the water is evaporating. More than that is a leak, and the difference is its rate: half an inch a day on a 16 by 32 pool is about 160 gallons a day.
How many gallons is an inch of pool water?
An inch over one square foot is 0.62 gallons, so multiply your surface area in square feet by 0.62. A 16 by 32 pool is 512 square feet, so an inch is about 319 gallons and a quarter inch about 80.
Why did my pool drop less than the bucket?
Something added water to the pool or took extra from the bucket. An autofill left on is the usual cause, then rain, then a bucket sitting warm on the deck. Fix it and run the test again.
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